DISCOVERY AND DISTRIBUTION OF ROOT LESION NEMATODE, PRATYLENCHUS NEGLECTUS, IN MONTANA by Wendy Ann Johnson A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Plant Pathology MONTANA STATE UNIVERSITY Bozeman, Montana November 2007 ©COPYRIGHT by Wendy Ann Johnson 2007 All Rights Reserved ii APPROVAL of a thesis submitted by Wendy Ann Johnson This thesis has been read by each member of the thesis committee and has been found to be satisfactory regarding content, English usage, format, citation, bibliographic style, and consistency, and is ready for submission to the Division of Graduate Education. Dr. Alan T. Dyer Approved for the Department Plant Sciences and Plant Pathology Dr. John Sherwood Approved for the Division of Graduate Education Dr. Carl A. Fox iii STATEMENT OF PERMISSION TO USE In presenting this thesis in partial fulfillment of the requirements for a master’s degree at Montana State University, I agree that the Library shall make it available to borrowers under rules of the Library. If I have indicated my intention to copyright this thesis by including a copyright notice page, copying is allowable only for scholarly purposes, consistent with “fair use” as prescribed in the U.S. Copyright Law. Requests for permission for extended quotation from or reproduction of this thesis in whole or in parts may be granted only by the copyright holder. Wendy Ann Johnson November 2007 iv ACKNOWLEDGEMENTS I would like to take this opportunity to express my upmost appreciation for the members of my committee. I’d like to thank them for their time and consideration on this project. I am especially thankful for the encouragement of my mentor and friend, Dr. Alan Dyer. I thank the members of the Dyer Lab for their expertise, energy in the field, and their friendly accommodation in the lab. I thank my husband Sam for his patience and his shared desire in my success. I also thank my parents, Alan and Cathy, for their generous support and for teaching me the biggest lessons, like the secret to a happy life is a full day of scooping silage. v TABLE OF CONTENTS 1. INTRODUCTION ...........................................................................................................1 2. ASSESSMENT OF ROOT LESION NEMATODE SPECIES AND DISTRIBUTION IN MONTANA ...................................................................................5 Introduction .....................................................................................................................5 Methods and Materials ....................................................................................................8 Results .............................................................................................................................9 Discussion .....................................................................................................................17 References .....................................................................................................................21 3. EVALUATION OF MONTANA SPRING WHEAT CULTIVARS FOR RESISTANCE AND TOLERANCE TO THE ROOT LESION NEMATODE, PRATYLENCHUS NEGLECTUS ..................................................................................24 Introduction ...................................................................................................................24 Methods and Materials ..................................................................................................26 Greenhouse Resistance Testing .............................................................................26 Tolerance Trials .....................................................................................................27 Statistical Analysis .................................................................................................28 Results ...........................................................................................................................28 Greenhouse Resistance Testing .............................................................................28 Tolerance Trials .....................................................................................................31 Discussion .....................................................................................................................33 References .....................................................................................................................36 4. CONCLUSIONS............................................................................................................39 APPENDICES ...............................................................................................................45 APPENDIX A: Bozeman Tolerance Vigor Data .......................................................46 APPENDIX B: Ulm Tolerance Trial Vigor Data ......................................................52 APPENDIX C: Bozeman Raw Yield Data ................................................................59 APPENDIX D: Ulm Raw Yield Data ........................................................................66 APPENDIX E: Greenhouse Resistance Trial Data 1 ................................................73 APPENDIX F: Greenhouse Resistance Trial Data 2 .................................................77 vi LIST OF TABLES Table Page 1. Incidence and average populations of root lesion and stunt nematodes for 17 counties sampled in Montana for 2006 ......................................................11 2. Incidence and average populations of root lesion and stunt nematodes for 15 counties sampled in Montana for 2007……………………………..........12 3. Multiplication factors for 16 of Montana’s modern and historic spring wheat cultivars as determined by greenhouse evaluations ...................................29 4. Tolerance indexes for Montana’s modern and historic spring wheat cultivars as determined by paired plot trials conducted in Bozeman and Ulm .......................................................................................................................33 vii LIST OF FIGURES Figure Page 1. Counties surveyed in 2006 (1A) and 2007 (1B) for root lesion nematode (P. neglectus) .....................................................................................................10 2. Comparison of root lesion nematode (P. neglectus) populations in 2006 (2A) and 2007 (2B) in no-till versus conventional, annual crop versus wheat fallow, and spring wheat versus winter wheat ...........................................14 3. Comparison of stunt nematode populations for 2006 (3A) and 2007 (3B) in no-till versus conventional, annual crop versus wheat fallow, and spring wheat versus winter wheat ...................................................................................16 4. Final root lesion nematode populations (P. neglectus) in greenhouse trial 1 (4A) and trial 2 (4B) for 16 of Montana’s historic and modern spring wheat cultivars ......................................................................................................30 viii ABSTRACT Root lesion nematodes (Pratylenchus neglectus and P. thornei) cause significant yield losses for wheat worldwide. To assess the prevalence of root lesion nematodes in Montana, soil samples were collected statewide in 2006 and 2007. In 2006, P. neglectus was found in 12 of the 17 counties and in 41% of all field samples surveyed. In 2007, P. neglectus was found in 11 of 15 counties and in 37% of all field samples surveyed. No P. thornei was found. For fields having root lesion nematode in 2006, P. neglectus mean population densities were 1213 nematodes/kg soil with population densities exceeding the damage threshold of 2500 nematodes/kg soil in 14% of the sampled fields. For fields having root lesion nematodes in 2007, P. neglectus mean population densities were 1303 nematodes/kg dry soil with densities exceeding the damage threshold of 2500 nematodes/kg dry soil in 13% of the samples. Damaging populations were restricted to the north central part of the state and were generally found in fields following a crop of winter wheat (p= 0.02). Stunt nematodes (Tylenchorynchus spp.) were detected in 93% and 85% of sampled fields for 2006 and 2007, respectively. New sources of tolerance and resistance to root lesion nematode are highly sought after due to limited breeding materials. Resistances of 16 cultivars were evaluated through inoculated greenhouse trials where multiplication of the pathogen was observed after 12 weeks of growth. No significant differences in multiplication factors (Rf= population final/population initial) were observed for the first trial (F test, p=0.11) though significant differences were evident between cultivars in the second trial (F test, p<0.001). From the greenhouse trials, the historic cultivar, Ceres was identified as a potentially useful source of nematode resistance. Tolerance evaluations were conducted at two nematode-infested sites (Ulm and Bozeman, MT) where the yield responses of 20 cultivars, with and without nematicide (Temik 15G ™) treatment, were compared. On average, nematicide treatments reduced yields at both sites (Ulm = 0.4% and Bozeman = 7.3%). No significant differences in nematode tolerances was detected among cultivars (Ulm, p=0.08; Bozeman, p=0.14). 1 CHAPTER 1 INTRODUCTION Root lesion nematodes, belonging to the genus Pratylenchus, are the third most agriculturally important group of nematodes in the United States, following cyst nematodes (Heterodera and Globodera)